Periodontal disease (PD) shares many common features with other human chronic inflammatory disease, such as rheumatoid arthritis, including production of autoantibodies, infiltration of lesions with plasma cells producing mainly IgG, and aberrant glycosylation of IgG-linked glycans. Particularly striking is the deficiency of galactose (Gal) in N-linked glycan side-chains on IgG molecules. Glycans have a profound effect on the biological activities of immunoglobulins (Ig). Deficiency of Gal residues renders such molecules pathogenic due to the fact that terminal N-acetylglucosamine residues, normally covered by Gal, became exposed and are recognized by the ubiquitous mannose-binding lectin resulting in the activation of complement with all the inflammatory consequences resulting in tissue damage. Based on considerable literature reports and our preliminary data, we propose to test the hypothesis that Ig-producing cells found in abundance in mononuclear cell infiltrates in PD secrete Ig molecules with aberrant glycosylation pattern of their glycan moieties. This in turn alters the biological properties of such Ig molecules with respect to their ability to activate complement and to interact with Fc receptors expressed on phagocytic cells resident in the inflamed lesions. Reduced glycosylation of Ig is likely to be due to the effect of cytokines locally produced by several cell types found in inflammatory lesions. Therefore, we propose the following Specific Aims: 1) Characterize the pattern of glycosylation aberrancies of Ig molecules in PD patients by reactivity with lectins highly specific for component monosaccharides and by direct carbohydrate analyses. 2) Determine the origin of aberrantly glycosylated Ig molecules by comparing glycosylation patterns of Ig in serum and lesions to determine whether Ig molecules with altered glycosylation are produced locally in the inflammatory lesions. 3) Determine if the aberrantly glycosylated Igs are specific for antigens of selected bacteria associated with PD. 4) Study mechanisms possibly involved in synthesis of Gal-deficient Ig in PD patients and the biological activities of Ig molecules with altered glycans. Results of these studies will generate information concerning previously unexplored inflammatory pathways that participate in the development of PD.